Im aware, from my years of lurking here, how many fanboys of TOS are here. As much as I love it, I view TOS as more of a nostalgia-trip than anything even close to TNG, DS9, VOY. It simply isn't as deep, as clever, as moving, as sharp...
As a reader of science-fiction, I appreciate what TOS did far more than what the spin-offs later did. They weren't afraid of any idea, no matter how outlandish it looked on paper. Sometimes it worked, sometimes it didn't. But that is why I find TOS to be one of the absolute best TV series of all time.
Modern Trek simply became 'very safe'. Very little of what was done during those twenty-five seasons fired my imagination the way the original Star Trek did.
Some of the tones in response to my comment is disappointing. I really dont think it is deserving of 'eye-rolls' or 'I need a drink' comments to say: 21 seasons of TNG, DS9 & VOY are far better than anything the 3 of TOS produced.
Be prepared for some ribbing no matter what statements you put forth here. This is a very eclectic collection of people with wildly varying viewpoints.